Bong-type smoking devices, i.e. water pipes are shown in the following prior U.S. patents.
______________________________________ Patentee Patent No. Issue Date ______________________________________ McFadden et al 3,881,499 May 6, 1975 Frost 3,882,875 May 13, 1975 Heggesteun 4,044,781 August 30, 1977 ______________________________________
These pipes have in common a reservoir partly filled with liquid, having a smoking-material bowl unit communicated via a tube to below the liquid level, a smoke-drawing tube communicated to the head-space of the reservoir, above the liquid level, and a need to be periodically cleaned in order to prevent souring of the reservoir and interior walls of the pipe with ash, residue and whatever the liquid removes from the gas stream.
In order to permit cleaning, various approaches have been tried. In McFadden et al there are several internal chambers, including one that is accessible by removal of a plug shown in FIG. 10 thereof and the others are made to have removable plugs or caps to facilitate cleaning.
Outside the smoking pipe art, the prior U.S. patent No. 3,365,093, of Malenke, issued Jan. 23, 1968 is for a neoprene plug which may be expanded into sealing engagement with a smooth-walled circular aperture in the wall of an internal combustion engine water jacket by the head of a bolt embedded in the plug and cooperating with a washer engaging a boss on the water jacket wall. The bolt shank extends through the outer face of the plug and threadably receives a nut thereon, engaging the washer.